1. Field of the Invention:
The invention relates to a mechanism for stabilizing a well tool in axially concentric relationship to the bore of a well conduit.
2. Summary of the Prior Art:
So-called centralizers have long been employed in subterranean wells for positioning a well tool in concentric relationship to the bore of a well conduit. Normally, such stabilizers take the form of a plurality of peripherally spaced, radially outwardly extending leaf spring elements which frictionally engage the bore of the well conduit. With this type of construction, the centralizer necessarily must be in frictional engagement with the well conduit both during run-in and during retrieval of the tool from the well conduit. Such friction not only produces undesirable wear on the centralizer but also on the bore wall of the conduit. Moreover, the speed of run-in or withdrawal is necessarily detrimentally affected.
U.K. Patent Application No. 2173533A discloses a stabilizer system employing radially expandable linkages each of which carries a roller on its radially outermost portions. The linkage is constantly spring urged to a radially expanded position and the rollers are thus in constant rolling engagement with the bore wall of the well conduit.
In recent years, a system has been developed for controlling downhole safety valves by electromagnetic waves radiated by a surface transmitter. Such system requires that a rod-like antenna be accurately centered in the well conduit at a position adjacent the electromagnetic wave receiving apparatus. If such antenna vibrates due to fluid flow around the antenna housing, the signal reception is subject to undesirable noise which may result in an erroneous signal transmittal to the safety valve control apparatus. It has been found that a more efficient and reliable stabilizer system is required by the aforementioned electromagnetic wave responsive control system than has been available in the prior art.